Abstract

We investigate dark-field imaging in the terahertz (THz) frequency regime with the intention to enhance image contrast through the analysis of scattering and diffraction signatures. A gold-on-TPX test structure and an archived biomedical tissue sample are examined in conventional and dark-field transmission geometry. In particular, the capability of the technique for tumor detection is addressed.

Figures (4)

(a) Experimental setup. Detected electric field without (b) and with (c) the beam stop placed into the beam. The thin lines show the signal enlarged by a factor of 100. (d) Power spectrum of the signal in (b). Absorption of water vapour is visible.

THz power-transmittance (a) and deflected-power (b) images of the edge test structure for various frequencies. In the bottom panels the location of the gold (black region) and TPX (white region) are indicated. (c) and (d): the corresponding line functions (the curves are shifted for visibility). THz power transmittance of the grid test structure (e) and detected dark-field signal (f) for various frequencies. In the bottom panels the layout of the grid test structure is indicated. Additionally, the calculated angle for the first-order diffraction pattern is listed (g).

(a) Optical image of the sample; (b) and (c): Total loss in transmission, (d) and (e): Loss induced by deflection; (f) and (g): Deflection coefficient. (h) Pulse duration (FWHM) of a low-frequency THz pulse. Click on Fig. 3(b,d,f) to see the data as a function of the frequency. (426 kB QuickTime movie)